Emergency Lights

[Tom Sutton]

The regulations talk about the emergency lights should operate in the event of mains failure, is that mains failure to the block of flats or mains failure to a particular circuit associated with the emergency light fitting i.e. on an maintained emergency fitting you have a switch line & permanent feed, however in some cases the emergency fitting is fed from a  two different points (the switch line is not on the same circuit as the permanent feed), so if the switch line failed the lights would not go into emergency, however if the block failed the lights would go in to emergency.

I received this enquiry today can somebody explain it so even I can understand.

[SeanW]

Hi,

The Emergency lighting ideally should be fed from the local lighting circuit.If it has a maintained switch supply then that also should be on the same circuit.The switch line is what it is, just a switch to turn between maintained & non maintained. If the switch line was fed from a separate circuit then you would raise the possibility of having 415VAC present.
If the system was a central battery unit you could have relays fed from the local distribution board which would changeover when that particular board had a mains failure and activate the slave emergency lights.

I hope this is of any use.

[John Webb]

There are three sorts of emergency lights:
Non-maintained - only comes on when the mains fails
Maintained - stays on all the time either mains or battery powered

The third type is a modification of the Maintained fittings - these are often fitted with a connection to allow them (particularly Exit Signs) to be switched off when the building is unoccupied. It is important that this connection comes from the same circuit that is powering the fittings and will probably need to be fused independently as well. See the maker's instructions.

Any emergency light must be supplied from the local lighting circuit only so that if just the one circuit fails the ELs in that area come on regardless of the state of the rest of the installation.

The only way in which modified Maintained fittings can be turned on and off remotely by a second circuit is if the fittings are each equipped with a small relay operated by the second circuit which switches the fitting's circuit within the fitting.

The central battery systems mentioned by SeanW are most common in theatres and some other public buildings such as hospitals and allow a much longer duration than the 3hrs of most self-contained fittings.

[Wiz]

twsutton, the point being made in the enquiry is that the two electrical feeds are coming from different sources.

This is the wrong way to connect the fitting because;

i) It may not operate on failure of the local electrical supply.

ii) Having two supplies is potentially dangerous as it may introduce a 415v supply.

The above is all as mentioned by Sean W and I am just confirming it.

[Galeon]

All you need to have is a phase failure monitor fitted ,and that will do the job for you , one thing I am finding is the misuse of maintained fittings , by having this fitted over a final exit door , it will be lit at all times (normally). All you are doing is burning the a*se out of the lamp and when you relay need it it could have failed.
IMO the old sustained version was a better choice to use.

[Tom Sutton]

It appears he is considering a maintained system in the common areas of blocks of flats but I would have thought a non-maintained system using self contained luminaires would be an acceptable system and would it be cheaper?

[CivvyFSO]

It would indeed be acceptable and it would indeed be cheaper.

I cannot see what the logic would be behind putting a maintained system in a block of flats. Pubs & nightclubs yes, flats no.

[nearlythere]

I cannot see what the logic would be behind putting a maintained system in a block of flats.

Comfort lighting of common areas?

[Tom Sutton]

Surely he could use the normal lighting for that purpose and leave it on 24/7 I think I am with Civvy on this one. I have asked him why but have not received any reply.